Temporary Loss of Servo Assist on Brakes

[transitgeorge]

Hi all I've just experienced what I consider a disturbing fault with my brakes. Went to use my van yesterday after a few days
park up and after turning it around (can't remember if I used the brakes or not but I did bump up and down off the kerb)
got to the junction at the end of the road, braked and the pedal was solid-no servo assist. Drove back to where I park
all the while testing brakes but still solid, so parked up for the night. This morning had a look at vac pipes etc but
couldn't see anything amiss so started engine and brakes were fine. Took it for a 10 mile run (gingerly with hand hovering
over handbrake) and they were still fine. Anyone else had the same or a similar experience or can shed any light on what may
have caused this? The van is an '03 mk6 2.0 75ps.
Thanks in advance
George